<%
        if(request.getAttribute("AllNodes")== null)
        {
                %>
        <script>
                alert("无法获取到树图节点");
        </script>        
                <%
                return;
        }
%>
<%
        List allNodes = (List)request.getAttribute("AllNodes");
%>
<%
        if(allNodes.size() == 0)
        {
                %>
        <script>
                alert("至少要设置一个根节点");
        </script>        
                <%
                return;                
        }
        TreeNode rootNode = (TreeNode)allNodes.get(0);
%>
